Abstract:

To provide a motor-driven valve with a small number of parts, with
excellent assemblage, capable of maintaining a large valve port diameter
even downsized, and to prevent deterioration of housing environment due
to sound caused by the impact and shortened life that are generated by
collisions of closing limit stopper parts. A motor-driven valve according
to the present invention comprises: a male screw member rotating in
accordance with a rotation of a rotor of an electric motor and engaging
with a female screw member fixed to a valve main body; a valve body
contacting to and separating from a valve seat in the valve main body by
a rotation of the male screw member; two stopper parts rotating in
accordance with the rotation of the rotor of the electric motor; an
opening limit stopper part mounted to the female screw member, the
opening limit stopper part contacting with one of the two stopper parts
in a fully-opened state of the motor-driven valve to restrict the
rotation of the male screw member in a direction that the motor-driven
valve opens; and a closing limit stopper part mounted to the female screw
member, the closing limit stopper part contacting with another stopper
part in a fully-closed state of the motor-driven valve to restrict the
rotation of the male screw member in a direction that the motor-driven
valve closes.

Claims:

1. A valve controller for detecting one of temperature and pressure of a
refrigeration cycle based on an output value of a sensor and controlling
valve opening of a motor-driven valve based on a detected value,
comprising:valve opening setting means for performing one of setting and
changing emergency valve opening of the motor-driven valve; andvalve
opening controlling means for stopping, when an abnormality occurs in the
sensor, movement of the motor-driven valve at an emergency valve opening
to which one of the setting and the changing is performed through the
valve opening setting means.

2. The valve controller as claimed in claim 1, wherein said emergency
valve opening is larger than a valve opening in a fully-closed state and
smaller than a valve opening in a fully-opened state, and is a valve
opening capable of continuing operation of the refrigeration cycle.

3. The valve controller as claimed in claim 1, wherein said sensor is one
of a temperature sensor for detecting temperature of a controlled object
and a pressure sensor for detecting pressure of a refrigerant circulating
in the refrigeration cycle.

4. The valve controller as claimed in claim 1, further comprising
communication means for performing one of the setting and the changing
the emergency valve opening from an outer device by utilizing one of wire
communication and wireless communication.

5. The valve controller as claimed in claim 1, wherein said motor-driven
valve is one of an expansion valve in the refrigeration cycle and a flow
control valve in a hot gas bypass circuit of the refrigeration cycle.

6. A valve controller for controlling valve opening of a motor-driven
valve and initialization processing of the motor-driven valve,
comprising:valve opening controlling means for controlling valve opening
of the motor-driven valve;initialization time setting means for setting
initialization time that determines intervals for performing the
initialization processing of the motor-driven valve;time measuring means
for measuring elapsed time; andinitialization controlling means for
performing the initialization processing of the motor-driven valve when
elapsed time that is measured by the time measuring means reaches to the
initialization time and the valve opening controlling means stops valve
opening control of the motor-driven valve as well.

7. The valve controller as claimed in claim 6, wherein said valve opening
controlling means calculates a deviation between a detected temperature
of an object to be adjusted for its temperature and a target
temperature;calculates a target valve opening based on the deviation;
andcontrols valve opening of the motor-driven valve so as to be the
target valve opening.

8. The valve controller as claimed in claim 7, wherein said motor-driven
valve is a motor-driven expansion valve in a refrigeration cycle, and
said detected temperature is a degree of superheat.

9. The valve controller as claimed in claim 8, wherein in said
refrigeration cycle are connected a compressor, a condenser, a
motor-driven valve and an evaporator in this order, and
operation/stoppage of the compressor is switched in accordance with a
temperature of a controlled object, andsaid initialization controlling
means performs the initialization processing of the motor-driven valve
when elapsed time that is measured by the time measuring means reaches to
the initialization time and the compressor stops as well.

10. The valve controller as claimed in claim 9, wherein said refrigeration
cycle is provided with a solenoid-operated valve disposed between the
condenser and the evaporator to open/close a refrigerant flow passage
between them;said valve controller is provided with solenoid-operated
valve controlling means for closing the solenoid-operated valve when
operation of the compressor stops and for opening the solenoid-operated
valve when operation of the compressor is restarted; andsaid
initialization controlling means performs initialization processing of
the motor-driven valve when elapsed time that is measured by the time
measuring means reaches to the initialization time and the
solenoid-operated valve is closed as well.

11. The valve controller as claimed in claim 10, wherein when the
solenoid-operated valve is closed said valve opening controlling means
maintains a valve opening of the motor-driven valve at an opening when
operation of the compressor stops, and when the solenoid-operated valve
is opened said valve opening controlling means starts valve opening
control of the motor-driven valve from the opening at the stoppage of the
compressor.

12. The valve controller as claimed in claim 6, further comprising
communication means for setting the initialization time from an outer
device by utilizing one of wire communication and wireless communication.

13. A valve controlling method of controlling valve opening of a
motor-driven valve as well as initialization processing of the
motor-driven valve, comprising the steps of:measuring elapsed time and
judging whether or not the measured elapsed time reaches to an
initialization time that determines intervals for performing the
initialization processing of the motor-driven valve; andperforming the
initialization processing of the motor-driven valve when said measured
elapsed time reaches to the initialization time, and valve opening
control of the motor-driven valve stops as well.

14. A refrigeration and cold storage system, in which a compressor, a
condenser, a motor-driven expansion valve and an evaporator are connected
in this order, said refrigeration and cold storage system switching
operation/stoppage of the compressor in accordance with a temperature of
a controlled object, and further comprising a solenoid-operated valve
disposed between the condenser and the evaporator to open/close a
refrigerant flow passage between them,wherein when operation of the
compressor is stopped, the solenoid-operated valve is closed and a valve
opening of the motor-driven expansion valve is maintained at an opening
when the operation of the compressor stops, and when the operation of the
compressor is restarted, the solenoid-operated valve is opened and valve
opening control of the motor-driven expansion valve starts from the
opening at the stoppage of the compressor.

15. A controller for controlling operation of a refrigeration and cold
storage system, said refrigeration and cold storage system having a
refrigeration cycle in which a compressor, a condenser, a motor-driven
expansion valve and an evaporator are connected in this order and a
solenoid-operated valve disposed between the condenser and the evaporator
to open/close a refrigerant flow passage between them, said refrigeration
and cold storage system switching operation/stoppage of the compressor in
accordance with a temperature of a controlled object,wherein said
controller, when stopping the operation of the compressor, closes the
solenoid-operated valve and maintains a valve opening of the motor-driven
expansion valve at an opening when the operation of the compressor stops,
and when restarting the operation of the compressor, opens the
solenoid-operated valve and starts valve opening control of the
motor-driven expansion valve from the opening at the stoppage of the
compressor.

16. The controller of the refrigeration and cold storage system as claimed
in claim 15, further comprising:a first control section for switching
operation/stoppage of the compressor in accordance with the temperature
of the controlled object and controlling opening/closing of the
solenoid-operated valve; anda second control section for controlling
valve opening of the motor-driven expansion valve in accordance with a
degree of superheat of a refrigerant flowing the evaporator,wherein said
second control section monitors opened/closed state of the
solenoid-operated valve and stops outputting a driving signal for the
valve opening control in accordance with the closing of the
solenoid-operated valve.

17. The controller of the refrigeration and cold storage system as claimed
in claim 16, wherein the first control section operates the compressor
when the temperature of the controlled object is higher or equal to a
first setting value that is set at a predetermined temperature, and the
first control section stops operation of the compressor when the
temperature of the controlled object is lower or equal to a second
setting value that is lower than the first setting value.

18. The controller of the refrigeration and cold storage system as claimed
in claim 15, wherein the refrigeration and cold storage system is used
for a refrigeration and cold storage showcase for foods, and the
temperature of controlled object is inside temperature of the
refrigeration and cold storage showcase.

19. A method of controlling operation of a refrigeration and cold storage
system, said refrigeration and cold storage system having a refrigeration
cycle in which a compressor, a condenser, a motor-driven expansion valve
and an evaporator are connected in this order and a solenoid-operated
valve disposed between the condenser and the evaporator to open/close a
refrigerant flow passage between them, said refrigeration and cold
storage system switching operation/stoppage of the compressor in
accordance with a temperature of a controlled object, wherein said method
comprising the steps of:when stopping the operation of the compressor,
closing the solenoid-operated valve and maintaining a valve opening of
the motor-driven expansion valve at an opening when the operation of the
compressor stops; andwhen restarting the operation of the compressor,
opening the solenoid-operated valve and starting valve opening control of
the motor-driven expansion valve from the opening at the stoppage of the
compressor.

[0004]The present invention relates to a valve controller for controlling
valve opening of a motor-driven valve, particularly to a controller for
valve opening control when an abnormality occurs in a temperature sensor,
a pressure sensor and the like. In addition, the present invention
relates to a valve controller and a valve controlling method,
particularly to a controller and so on for controlling valve opening of a
motor-driven valve and others for adjusting flow rate of a refrigerant.
Further, the present invention relates to a refrigeration and cold
storage system used for a refrigeration and cold storage show case and so
on, and a device and a method for controlling the system, particularly to
a refrigeration and cold storage system and the like in which
operation/stoppage of a compressor is switched in accordance with a
temperature of a controlled object.

[0005]2. Description of the Related Art

[0006]Conventionally, in a refrigeration cycle used for refrigeration and
cold storage show cases and the others, in order to accurately adjust
flow rate of a circulating refrigerant, as an expansion valve for flow
control, a motor-driven valve with a pulse motor for moving a valve body
has widely been utilized. In this refrigeration cycle, generally, a
degree of superheat is calculated after detecting inlet and outlet
temperatures of an evaporator with temperature sensors, and valve opening
of the motor-driven valve is controlled by comparing the calculated
degree of superheat with a preliminarily set degree of superheat.

[0007]As described above, although the valve opening control of the
motor-driven valve is performed based on the temperature detected by the
temperature sensor, at the operation of the refrigeration cycle, there is
a possibility that the temperature cannot appropriately be detected when
an abnormality occurs in the temperature sensor due to disconnection,
short circuit and the like in operation, in such case, it becomes
impossible to continue the valve opening control of the motor-driven
valve also. Then, in a conventional valve controller, in its
manufacturing stage, a fully-closed value or a fully-opened value is set
as an opening value for emergency, when an abnormality occurs in the
temperature sensor, the motor-driven valve is controlled to stop in the
fully-closed or fully-opened state (see Patent document 1 as an example).

[0008]But, when the motor-driven valve is stopped in the fully-closed
state, after that, all the while, a refrigerant does not flow in the
refrigeration cycle, so that the operation of the refrigeration cycle
stops due to a low-pressure abnormality, which makes it impossible, as an
example, to maintain inside temperature of a refrigeration and cold
storage show case low. As a result, until a maintenance worker arrives,
the inside temperature remains high over a long period of time, resulting
in bruised foods.

[0009]On the other hand, in case that the motor-driven valve is stopped in
the fully-opened state, circulation of the refrigerant is not stopped but
the quantity of refrigerant fed to the evaporator becomes too much, so
that a refrigerant from the evaporator is returned to the compressor in
the form of liquid (liquid back). In this case also, the show case cannot
be cooled in the same manner as described above, which may cause bruised
foods, moreover, there is a fear that the compressor is damaged through
liquid compression.

[0010]These problems can be generated not only when an abnormality occurs
in the temperature sensor but in a pressure sensor for detecting pressure
of a refrigerant circulating in the refrigeration cycle almost in the
same manner as described above, so that it has been a key problem to
consider a measure in case of abnormality in the sensors for detecting
temperature and pressure in the refrigeration cycle.

[0011]Further, conventionally, in refrigeration cycle systems used for
air-conditioners, refrigeration and cold storage show cases, and the
like, flow rate of a circulating refrigerant is adjusted for the purposes
of stabilizing a cooling capacity, efficient operation, and the like, and
in order to accurately performing the adjustment, as an expansion valve
for controlling the flow rate, a motor-driven valve that is a
motor-driven expansion valve with a pulse motor for moving the valve body
has been widely utilized.

[0012]However, since the valve opening control of the motor-driven valve
is generally performed with an open-loop control that doesn't feed back
an absolute opening (actual opening), in addition, when a power-supply to
the motor-driven valve is stopped, the valve body in the motor-driven
valve stops at a position when the power-supply is stopped without
returning to an initial position, so that at and after the second a
power-supply after the first supply, it is impossible to exactly grasp an
absolute opening (a position of the valve body) when the power-supply is
started.

[0013]Therefore, in the control of the motor-driven valve, generally, an
initialization processing is performed when power is supplied to the
valve, and the valve opening control is started after determining the
initial position of the valve body (for instance, see Patent document 2).
Here, it is the initialization processing to drive the motor-driven valve
so as to be closed by applying the number of pulses over all the strokes
from the fully-opened state to the fully-closed state to forcibly change
the valve opening of the motor-driven valve to that in fully-closed
state.

[0014]However, in the refrigeration cycle system, there is a possibility
that foreign substances such as impure substances are generated in a
refrigerant flow passage, in the foreign substances, large ones can be
removed by a strainer and so on, but small ones may pass through the
strainer and flow into the inside of the motor-driven valve. In such a
case, in the motor-driven valve are caught the foreign substances, which
may cause a shift in the valve opening of the valve.

[0015]That is, in case that the catching of the foreign substance occurs,
since the foreign substance prevents the valve body from moving, for
example, when a driving signal of 100 pulses are added to the pulse
motor, an actual amount to be driven becomes smaller than that when
driving the signal of 100 pulses are given. As a result, a difference of
several pulses is generated between a valve opening estimated from the
number of pulses added to the motor-driven valve and an actual valve
opening of the motor-driven valve itself, after that, the motor-driven
valve is operated with the valve opening including the difference.

[0016]For this reason, it becomes impossible to accurately control the
valve opening of the motor-driven valve, for instance, when a driving
signal for obtaining the fully-closed state is added to the motor-driven
valve, the motor-driven valve is actually in a slightly-opened state. In
this case, it is possible to generate a leak of a refrigerant and the
like, resulting in deteriorated reliability of the device and so on.

[0017]Further, generally, in the refrigeration and cold storage show cases
utilized for cold reserving and displaying foods and the like,
operation/stoppage of the compressor is switched in accordance with
high/low of the inside temperature, and the switching action is repeated
according to the change in the inside temperature, which controls the
inside temperature to be maintained constant.

[0018]The switching of the operation/stoppage of the compressor is
performed in such a manner that the compressor is operated at the moment
that the inside temperature becomes higher or equal to a predetermined
setting temperature for turning the compressor on, and the operation of
the compressor is stopped at the moment that the inside temperature
becomes lower or equal to a predetermined setting temperature for turning
the compressor off. A difference between the setting temperatures for
turning the compressor on/off is called "DIFFERENTIAL", which is set to
avoid frequent operation/stoppage actions (hunting) of the compressor.

[0019]In addition, flow rate of a circulating refrigerant in the
refrigeration cycle is adjusted for the purposes of stabilization of a
cooling capacity when cooling inside of a refrigeration and cold storage
showcase, efficient operation, and the like, and in order to accurately
performed the adjustment, as a flow control valve for the refrigerant, a
motor-driven expansion valve with a pulse motor or the like has widely
been used. In the refrigeration cycle with the motor-driven expansion
valve, a degree of superheat of a refrigerant flowing the evaporator is
detected, and the detected degree of superheat is compared with a setting
degree of superheat, and in accordance with the difference, the flow rate
of the refrigerant is controlled through adjustment of the valve opening
of the motor-driven expansion valve using a PID control and others.

[0020]By the way, as described above, when operation/stoppage of the
compressor is switched, according to this motion of the compressor,
opening/closing of the expansion valve needs to be controlled. As a
method of controlling the valve, for example, in the Patent document 3 is
disclosed a technique that at the stoppage of the compressor is
controlled the motor-driven expansion valve so as to be fully-closed
once, and a predetermined period of time later, the valve is fully-opened
to uniform gas pressure in a refrigeration cycle, and when starting the
operation of the compressor, the valve opening of the valve is set to be
an initial opening (preliminarily set standard opening) or a memorized
opening (the valve opening just before the compressor stops).

[0021]The technique disclosed in the Patent document 3 is applied to air
conditioners for adjusting room temperature, so that the gas pressure in
the cycle is uniformed in the fully-opened state, on the contrary, in
refrigeration and cold storage show cases, to avoid increasing the inside
temperature, the uniformity of the gas pressure at the stoppage of the
compressor is not carried out in general. For this reason, in case that
the technique described above is applied to the control of the
refrigeration and cold storage show cases, when the compressor is
stopped, the valve opening of the motor-driven expansion valve is
controlled to be the fully-closed state, and the valve opening is set to
be the initial opening or the memorized opening when starting the
operation of the compressor.

[0022]However, as described above, in case that the valve opening of the
motor-driven expansion valve is switched between the fully-closed opening
and the initial opening (or the memorized opening) in accordance with the
operation/stoppage of the compressor, in each switching
operation/stoppage of the compressor, the valve opening of the valve is
to be changed with great operation amount.

[0023]In addition, in the refrigeration and cold storage show cases, the
number of switching of the operation/stoppage of the compressor is
comparatively large, there are quite a few case that is required a heavy
switching action repeating operation/stoppage at five minute intervals.
In such a case, the number of switching operation/stoppage of the
compressor is more than ten times an hour, resulting in seriously
increased driving frequency of the motor-driven expansion valve.

[0024]Further, the motor-driven expansion valve is a machine component
with sliding parts, so that as the driving frequency increases, abrasion
of the sliding parts advances to shorten the life of the valve, and its
durability life is generally defined in terms of the number of the
driving pulses added to the pulse motor. For this reason, when the number
of driving pulses added to the pulse motor is considerably increased by
changing the valve opening as described above, remaining number of pulses
defined as the durability life are rapidly consumed, resulting in
shortened life of the motor-driven expansion valve. As a result, frequent
replacements of the motor-driven expansion valve are forced to be carried
out, consequently, generating a problem of decreased reliability of the
refrigeration and cold storage show cases.

[0028]The present invention has been made in consideration of the
problems, and the object thereof is to provide a valve controller and
others capable of improving reliability of refrigeration systems and
lengthening life of the systems.

[0029]In detail, the object of the present invention is to appropriately
control valve opening of a motor-driven valve and to prevent damage of a
controlled object for its temperature when an abnormality occurs in a
temperature sensor, a pressure sensor or the like, and also the object is
to appropriately modify a difference in the valve opening of the
motor-driven valve caused by a catching of a foreign substance or the
like and to prevent a trouble such as refrigerant leakage. Further, the
object of the present invention is to prevent the number of driving
pulses of a driving signal for driving a motor-driven valve from
excessively increasing under a condition that operation/stoppage of a
compressor is frequently switched to lengthen the life of the
motor-driven valve, consequently, to improve reliability of the
refrigeration and cold storage system itself.

[0030]To achieve the above object, the present invention relates to a
valve controller for detecting one of temperature and pressure of a
refrigeration cycle based on an output value of a sensor and controlling
valve opening of a motor-driven valve based on a detected value, and the
valve controller is characterized by comprising: valve opening setting
means for performing one of setting and changing an emergency valve
opening of the motor-driven valve; and valve opening controlling means
for stopping, when an abnormality occurs in the sensor, movement of the
motor-driven valve at an emergency valve opening to which one of the
setting and the changing is performed through the valve opening setting
means.

[0031]With the valve controller of the present invention, when an
abnormality occurs in the sensor the motor-driven valve is stopped at the
set or changed emergency valve opening, so that setting an intermediate
valve opening, as the emergency valve opening, between the valve openings
in the fully-opened and the fully-closed states, as an example, prevents
the refrigeration cycle from unintentionally stopping. As a result, even
when a prompt repair work cannot be conducted it becomes possible to
prevent the object to be managed for its temperature from being damaged.
In addition, the emergency valve opening can freely be set or changed,
which allows the emergency valve opening to suitably be set in accordance
with usage of the refrigeration cycle and user's request, resulting in a
refrigeration cycle with improved flexibility and convenience.

[0032]In the valve controller as described above, the emergency valve
opening can be larger than a valve opening in a fully-closed state and
smaller than a valve opening in a fully-opened state, and may be a valve
opening capable of continuing operation of the refrigeration cycle.

[0033]In the above valve controller, the sensor may be one of a
temperature sensor for detecting temperature of a controlled object and a
pressure sensor for detecting pressure of a refrigerant circulating in
the refrigeration cycle.

[0034]It is possible that the valve controller described above further
comprises communication means for performing one of setting and changing
the emergency valve opening from an outer device by utilizing one of wire
communication and wireless communication.

[0035]Further, in the above valve controller, the motor-driven valve may
be one of an expansion valve in the refrigeration cycle and a flow
control valve in a hot gas bypass circuit of the refrigeration cycle.

[0036]Still further, the present invention relates to a valve controller
for controlling valve opening of a motor-driven valve and initialization
processing of the motor-driven valve, the valve controller is
characterized by comprising: valve opening controlling means for
controlling valve opening of the motor-driven valve; initialization time
setting means for setting initialization time that determines intervals
for performing the initialization processing of the motor-driven valve;
time measuring means for measuring elapsed time; and initialization
controlling means for performing the initialization processing of the
motor-driven valve when elapsed time that is measured by the time
measuring means reaches to the initialization time and the valve opening
controlling means stops valve opening control of the motor-driven valve
as well.

[0037]With the valve controller of the present invention, the
initialization time can be set, and each time the elapsed time that is
measured by the time measuring means reaches to the initialization time,
the initialization processing of the motor-driven valve is performed, so
that not only at the power-up but after that, the initialization
processing can periodically be carried out. As a result, even when a
difference in valve opening caused by catching of a foreign substance or
the like is generated, the difference can periodically be modified, which
allows the valve opening of the motor-driven valve to accurately be
controlled.

[0038]In addition to the above, the initialization processing is performed
only at the stoppage of the valve opening control of the motor-driven
valve, so that the initialization processing can be performed without
harmful effect to the valve opening control of the motor-driven valve. As
a result, it is unnecessary to stop the operation of devices for the
initialization processing, which allows hindrance to the operation of
devices to be avoided and complexity accompanying the operation to be
eliminated as well.

[0039]In the above valve controller, it is possible that the valve opening
controlling means calculates a deviation between a detected temperature
of an object to be adjusted for its temperature and a target temperature;
calculates a target valve opening based on the deviation; and controls
valve opening of the motor-driven valve so as to be the target valve
opening.

[0040]In the valve controller described above, the motor-driven valve can
be a motor-driven expansion valve in a refrigeration cycle, and the
detected temperature may be a degree of superheat.

[0041]In the valve controller, it is possible that in the refrigeration
cycle are connected a compressor, a condenser, a motor-driven valve and
an evaporator in this order, and operation/stoppage of the compressor is
switched in accordance with a temperature of a controlled object, and the
initialization controlling means performs the initialization processing
of the motor-driven valve when elapsed time that is measured by the time
measuring means reaches to the initialization time and the compressor
stops as well.

[0042]Further, in the valve controller, it is possible that the
refrigeration cycle is provided with a solenoid-operated valve disposed
between the condenser and the evaporator to open/close a refrigerant flow
passage between them, and the valve controller is provided with
solenoid-operated valve controlling means for closing the
solenoid-operated valve when operation of the compressor stops and for
opening the solenoid-operated valve when operation of the compressor is
restarted, and the initialization controlling means performs
initialization processing of the motor-driven valve when elapsed time
that is measured by the time measuring means reaches to the
initialization time and the solenoid-operated valve is closed as well.

[0043]In the valve controller, when the solenoid-operated valve is closed
the valve opening controlling means may maintain a valve opening of the
motor-driven valve at an opening when operation of the compressor stops,
and when the solenoid-operated valve is opened the valve opening
controlling means can start valve opening control of the motor-driven
valve from the opening at the stoppage of the compressor. With this, the
operation amount of the motor-driven valve accompanying switching of
operation/stoppage of the compressor can be small, which makes it
possible to lengthen the life of the motor-driven valve.

[0044]Further, the valve controller described above may further comprises
communication means for setting the initialization time from an outer
device by utilizing one of wire communication and wireless communication.

[0045]Still further, the present invention relates to a valve controlling
method of controlling valve opening of a motor-driven valve as well as
initialization processing of the motor-driven valve, and the method is
characterized by comprising the steps of: measuring elapsed time and
judging whether or not the measured elapsed time reaches to an
initialization time that determines intervals for performing the
initialization processing of the motor-driven valve; and performing the
initialization processing of the motor-driven valve when the measured
elapsed time reaches to the initialization time, and valve opening
control of the motor-driven valve stops as well.

[0046]Further, the present invention relates to a refrigeration and cold
storage system, in which a compressor, a condenser, a motor-driven
expansion valve and an evaporator are connected in this order, the
refrigeration and cold storage system switching operation/stoppage of the
compressor in accordance with a temperature of a controlled object,
further comprising a solenoid-operated valve disposed between the
condenser and the evaporator to open/close a refrigerant flow passage
between them, wherein when operation of the compressor is stopped the
solenoid-operated valve is closed and a valve opening of the motor-driven
expansion valve is maintained at an opening when the operation of the
compressor stops, and when the operation of the compressor is restarted
the solenoid-operated valve is opened and valve opening control of the
motor-driven expansion valve starts from the opening at the stoppage of
the compressor.

[0047]With the refrigeration and cold storage system of the present
invention, the solenoid-operated valve is disposed between the condenser
and the evaporator, and when operation of the compressor is stopped the
solenoid-operated valve is closed and the valve opening of the
motor-driven expansion valve is maintained at the opening when the
operation of the compressor stops, and when the operation of the
compressor is restarted the solenoid-operated valve is opened and the
valve opening control of the motor-driven expansion valve starts from the
opening at the stoppage of the compressor, which makes it possible that
operations for fully-closing the motor-driven expansion valve at the
stoppage of the compressor and opening the motor-driven expansion valve
at the start of the compressor are unnecessary while preventing inside
temperature at the stoppage of the compressor from increasing. As a
result, it becomes unnecessary to largely change the valve opening of the
motor-driven expansion valve each time the operation/stoppage of the
compressor is switched, which remarkably reduces the consumption of the
number of driving pulses. This allows the life of the motor-driven
expansion valve to be lengthened, consequently, the reliability of the
refrigeration and cold storage system to be improved.

[0048]Further, the present invention relates to a controller for
controlling motion of a refrigeration and cold storage system, the
refrigeration and cold storage system having a refrigeration cycle in
which a compressor, a condenser, a motor-driven expansion valve and an
evaporator are connected in this order and a solenoid-operated valve
disposed between the condenser and the evaporator to open/close a
refrigerant flow passage between them, the refrigeration and cold storage
system switching operation/stoppage of the compressor in accordance with
a temperature of a controlled object, wherein the controller, when
stopping the operation of the compressor, closes the solenoid-operated
valve and maintains valve opening of the motor-driven expansion valve at
an opening when the operation of the compressor stops, and when
restarting the operation of the compressor, opens the solenoid-operated
valve and starts valve opening control of the motor-driven expansion
valve from the opening at the stoppage of the compressor.

[0049]With the present invention, in the same manner as the above
inventions, even when the operation/stoppage of the compressor is
frequently switched, it is possible to prevent the number of driving
pulses of the driving signal for driving the motor-driven expansion valve
from becoming considerably large, which lengthens the life of the valve,
consequently, improves the reliability of the refrigeration and cold
storage system itself.

[0050]The controller of the refrigeration and cold storage system may
further comprises: a first control section for switching
operation/stoppage of the compressor in accordance with the temperature
of the controlled object and controlling opening/closing of the
solenoid-operated valve; and a second control section for controlling
valve opening of the motor-driven expansion valve in accordance with a
degree of superheat of a refrigerant flowing the evaporator, wherein the
second control section monitors opened/closed state of the
solenoid-operated valve and stops outputting a driving signal for the
valve opening control in accordance with the closing of the
solenoid-operated valve.

[0051]In the controller of the refrigeration and cold storage system, the
first control section operates the compressor when the temperature of the
controlled object is higher or equal to a first setting value that is set
at a predetermined temperature, and the first control section stops
operation of the compressor when the temperature of the controlled object
is lower or equal to a second setting value that is lower than the first
setting value.

[0052]In the controller of the refrigeration and cold storage system, the
refrigeration and cold storage system is used for a refrigeration and
cold storage showcase for foods, and the temperature of controlled object
is an inside temperature of the refrigeration and cold storage showcase.

[0053]Further, the present invention relates to a method of controlling
motion of a refrigeration and cold storage system, the refrigeration and
cold storage system having a refrigeration cycle in which a compressor, a
condenser, a motor-driven expansion valve and an evaporator are connected
in this order and a solenoid-operated valve disposed between the
condenser and the evaporator to open/close a refrigerant flow passage
between them, the refrigeration and cold storage system switching
operation/stoppage of the compressor in accordance with a temperature of
a controlled object, wherein the method comprising the steps of: when
stopping the operation of the compressor, closing the solenoid-operated
valve and maintaining a valve opening of the motor-driven expansion valve
at an opening when the operation of the compressor stops; and when
restarting the operation of the compressor, opening the solenoid-operated
valve and starting valve opening control of the motor-driven expansion
valve from the opening when the operation of the compressor is stopped.

[0054]As described above, with the present invention, it becomes possible
to provide a valve controller and others capable of improving reliability
of refrigeration systems and lengthening life of the systems.

[0055]In detail, it is possible to appropriately control valve opening of
a motor-driven valve and to prevent damage of a controlled object for its
temperature when abnormality occurs in a temperature sensor, a pressure
sensor or the like, and also it is possible to appropriately modify a
difference in the valve opening of the motor-driven valve caused by a
catching of a foreign substance or the like and to prevent a trouble such
as refrigerant leakage. Further, it is possible to prevent the number of
driving pulses of a driving signal for driving a motor-driven valve from
excessively increasing under a condition that operation/stoppage of a
compressor is frequently switched to lengthen the life of the
motor-driven valve, consequently, to improve reliability of the
refrigeration and cold storage system itself.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056]The present invention will be more apparent from the ensuring
description with reference to the drawings, wherein:

[0057]FIG. 1 is a drawing showing the construction of an example of a
refrigeration cycle system with a valve controller according to the first
embodiment of the present invention;

[0058]FIG. 2 is a block diagram showing a degree-of-superheat controller
shown in FIG. 1 and peripheral circuits around the controller in detail;

[0059]FIG. 3 is a flow chart for explaining interrupt processing of a
temperature controller;

[0060]FIG. 4 is a flow chart for explaining interrupt processing of the
degree-of-superheat controller;

[0061]FIG. 5 is an appearance diagram showing surface of a main body of
the degree-of-superheat controller;

[0062]FIG. 6 is a flow chart for explaining operations of inputting and
changing a setting value;

[0063]FIG. 7 is a drawing showing the construction of an example of a
refrigeration cycle system with a valve controller according to the
second embodiment of the present invention;

[0064]FIG. 8 is a block diagram showing a degree-of-superheat controller
shown in FIG. 7 and peripheral circuits around the controller in detail;

[0065]FIG. 9 is a flow chart for explaining a managing procession of
initialization timing;

[0066]FIG. 10 is a flow chart for explaining interrupt processing of the
degree-of-superheat controller;

[0067]FIG. 11 is a timing diagram showing an example of the operation of
the refrigeration cycle system under control shown in FIGS. 3, 9 and 10;

[0068]FIG. 12 is a drawing showing the construction of a refrigeration and
cold storage system according to the third embodiment of the present
invention;

[0069]FIG. 13 is a flow chart for explaining control operation of a
degree-of-superheat controller shown in FIG. 12; and

[0070]FIG. 14 is a timing diagram showing an example of operations of a
solenoid-operated valve and a motor-driven valve when operation/stoppage
of a compressor is switched.

DETAILED DESCRIPTION OF THE INVENTION

[0071]A valve controller according to the first embodiment of the present
invention will be explained with reference to FIGS. 1 to 6. Here, as a
refrigeration cycle system is exemplified a system for controlling
temperature inside a refrigeration and cold storage showcase used for
cold reserving and displaying foods, in addition, the valve controller of
the present invention is exemplarily used for a device for controlling an
expansion valve (motor-driven valve) disposed in the above refrigeration
cycle system.

[0072]FIG. 1 shows the refrigeration cycle system with the valve
controller according to the present invention, and the system 1 is
provided with a compressor 2, a condenser 3, a condenser fan 3a, a
solenoid-operated valve 4, a motor-driven valve 5, an evaporator 6, an
evaporator fan 6a, an inlet temperature sensor 7, an outlet temperature
sensor 8, an inside temperature sensor 9, a temperature controller 10 and
a degree-of-superheat controller 11.

[0073]The compressor 2, the condenser 3, the solenoid-operated valve 4,
the motor-driven valve 5 and the evaporator 6 are connected with each
other through a conduit 12, and among them circulates a refrigerant.
Here, the quantity of the refrigerant flowing through the conduit 12 is
controlled by adjusting valve opening of the motor-driven valve 5.

[0074]The compressor 2 compresses the refrigerant in low pressure gas
state fed from the evaporator 6 and changes it into high pressure gas
state so as to be fed to the condenser 3 through the conduit 12.

[0075]The condenser 3 condenses the refrigerant in high pressure gas state
fed from the compressor 2 to change it into a refrigerant in high
pressure liquid state with condensation heat being removed, and the
condenser 3 releases the removed heat to outside through air blow by the
condenser fan 3a.

[0076]The solenoid-operated valve 4 is installed to open/close a
refrigerant flow passage 12a between the condenser 3 and the evaporator 6
and to change flow/non-flow of the refrigerant into the evaporator 6.
This solenoid-operated valve 4 operates depending on a solenoid-operated
valve driving signal SV outputted from the temperature controller 10, and
the valve 4 opens/closes in accordance with a voltage level of the
solenoid-operated valve driving signal SV.

[0077]The motor-driven valve 5 changes the refrigerant in high pressure
liquid state fed from the condenser 3 into low pressure state. This valve
5 is provided with a built-in pulse motor 5a (shown in FIG. 2) that is
driven in accordance with a motor-driven valve driving signal EV from the
degree-of-superheat controller 11, and the valve opening of the valve 5
is adjusted by the rotation of the pulse motor 5a with rotational angles
in accordance with the number of pulses of the motor-driven valve driving
signal EV.

[0078]The evaporator 6 is provided to evaporate (vaporize) the refrigerant
in low pressure liquid state, and the refrigerant removes evaporation
heat from its circumference through the evaporation, and is heated. At
this moment, the removed heat cools ambient air around the evaporator 6,
and the cooled air is released by the air blow by the evaporator fan 6a
to adjust temperature inside the refrigeration and cold storage show
case.

[0079]The inlet temperature sensor 7, the outlet temperature sensor 8 and
the inside temperature sensor 9 detect a temperature Tin of the
refrigerant at the inlet of the evaporator 6 (the refrigerant in liquid
state), a temperature Tout of the refrigerant at the outlet of the
evaporator 6 (the refrigerant in gas state) and a temperature Tis inside
the refrigeration and cold storage show case respectively. These sensors
7 to 9 are constructed by thermistors with negative
temperature-resistance characteristic for instance.

[0080]The temperature controller 10 is a control circuit for adjusting
temperature inside the refrigeration and cold storage show case by
controlling operation/stoppage of the compressor 2, and is constructed,
for example, by a microcomputer and peripheral circuits (both of them are
not shown). The temperature controller 10 compares the inside temperature
Tis detected by the inside temperature sensor 9 and a preliminarily set
temperature Ton for turning on the compressor 2 (hereinafter called as
"ON set temperature"), and a preliminarily set temperature Toff for
turning off the compressor 2 (hereinafter called as "OFF set
temperature") with each other, and in accordance with the results,
controls the operation/stoppage of the compressor 2. And, between the ON
set temperature Ton and the OFF set temperature Toff is set a
"DIFFERENTIAL (difference in temperature)" to avoid frequent
operation/stoppage actions (hunting) of the compressor 2.

[0081]In addition, the temperature controller 10 has a function of
controlling opening/closing of the solenoid-operated valve 4 in
accordance with an operating condition of the compressor 2 also, and the
opening/closing control of the valve 4 is performed through the
solenoid-operated valve driving signal SV. This solenoid-operated valve
driving signal SV is set at a voltage level (for example AC 200V) for
opening the solenoid-operated valve 4 while the compressor 2 is in
operation, on the other hand, the signal SV is set at a voltage level
(for example 0V) for closing the solenoid-operated valve 4 while the
compressor 2 is in stoppage.

[0082]The degree-of-superheat controller 11 is a control circuit for
controlling valve opening of the motor-driven valve 5, and is
constructed, for example, by a microcomputer and peripheral circuits in
the same manner as the temperature controller 10. This controller 11
calculates valve opening of the motor-driven valve 5 through a PID
control based on a degree of superheat Tsh of the refrigerant in the
evaporator 6 (the temperature Tout detected by the outlet temperature
sensor 8-the temperature Tin detected by the inlet temperature sensor 7),
and outputs the motor-driven valve driving signal EV corresponding to the
calculated valve opening to the pulse motor 5a of the motor-driven valve
5.

[0083]In addition, the degree-of-superheat controller 11 has a function of
monitoring abnormality in the inlet temperature sensor 7 and the outlet
temperature sensor 8 also, in case that outputs of these temperature
sensor 7, 8 are abnormal, the controller 11 changes the valve opening of
the motor-driven valve 5 to a preliminarily set emergency valve opening
SP. Further, as will hereinafter be described in detail, the emergency
valve opening SP can be set any value by one pulse by users.

[0085]The inlet temperature detecting circuit 14 is a resistance-voltage
conversion circuit that converts a resistance value of the inlet
temperature sensor 7 to a DC-voltage signal and outputs it to the micro
processor 13. This inlet temperature detecting circuit 14 provides an
electric signal (inlet temperature signal) corresponding to the
temperature Tin of the refrigerant at the inlet of the evaporator 6 to
the micro processor 13.

[0086]The outlet temperature detecting circuit 15 is a resistance-voltage
conversion circuit that converts a resistance value of the outlet
temperature sensor 8 to a DC-voltage signal and outputs it to the micro
processor 13. This outlet temperature detecting circuit 15 provides an
electric signal (outlet temperature signal) corresponding to the
temperature Tout of the refrigerant at the outlet of the evaporator 6 to
the micro processor 13.

[0087]The input circuit 17 is disposed to input a set degree of superheat
(target temperature) Ts, upper and lower opening limits of the
motor-driven valve 5 (for instance, when the motor-driven valve 5 is used
with 100 pulses to 400 pulses, the upper opening limit is set to be 400
pulses and the lower opening limit to be 100 pulses), each coefficient
for P (proportional), I (integral) and D (differential) at a PID control,
the emergency valve opening SP and so on. These varieties of input values
can be set as setting values, and the setting values set can be changed
with the input circuit 17 also. Methods of setting the input value and
changing the setting value will be explained below in detail.

[0088]This input circuit 17 is provided with four tact switches 17a to 17d
(an up switch 17a, a down switch 17b, a set switch 17c and an enter
switch 17d), and ON/OFF states of the tact switches 17a to 17d are
outputted to the micro processor 13.

[0089]The display circuit 18 is provided with a temperature displaying
element 18a, a valve opening displaying element 18b and a plurality of
LEDs 18c. The temperature displaying element 18a displays the refrigerant
temperature Tin at the inlet and the refrigerant temperature Tout at the
outlet of the evaporator 6, and the degree of superheat Tsh (=Tout-Tin)
while switching them, and in a setting mode, setting values of the set
degree of superheat Ts, the upper opening limit, the lower opening limit,
the emergency valve opening SP and others are displayed. In addition, the
valve opening displaying element 18b displays the present valve opening
of the motor-driven valve 5 by the number of pulses from the fully-closed
state.

[0090]The plurality of LEDs 18c turn on in relation to displayed items of
the temperature displaying element 18a and the valve opening displaying
element 18b, and consist of six LEDs from "degree of superheat" to
"alarm". Each LED for "degree of superheat", "inlet" and "outlet" shows a
displayed item of the temperature displaying element 18a and turns on in
relation to the temperature displayed on the temperature displaying
element 18a. Further, the LED for "setting" turns on when the
degree-of-superheat controller 11 is in a setting mode, and the LED for
"drive" turns on when the controller 11 is in operation. The LED for
"alarm" turns on when an output data of the inlet temperature sensor 7 or
the outlet temperature sensor 8 is abnormal.

[0091]The display driver circuit 19 amplifies a signal from the micro
processor 13 and outputs the amplified signal to the display circuit 18.
The memory circuit 20 stores the above setting values and so on for
backing up.

[0092]The motor-driven valve driving circuit 16 is disposed to amplify a
driving control signal from the micro processor 13 and to output driving
pulses to the pulse motor (stepping motor) 5a built in the motor-driven
valve 5, and is provided with a driver IC (integrated circuit) (driving
signal amplifying circuit) 16a, etc.

[0093]The micro processor 13 is provided with an A/D converter 13a, a CPU
(Central Processing Unit) 13b, a ROM 13c, a RAM 13d, a timer 13e, an I/O
(13f) and so on.

[0094]The A/D converter 13a converts analog signals on temperature
outputted from the inlet temperature detecting circuit 14 and the outlet
temperature detecting circuit 15 into digital signals, and the CPU 13b
interprets and executes programs stored in the ROM 13c. The ROM 13c is a
nonvolatile memory storing an operation program for executing valve
opening control by PID control operation described below, a program for
controlling valve opening of the motor-driven valve 5 when an abnormality
occurs in the temperature sensors 7,8, a display control program and so
on. The RAM 13d functions as a work memory of the CPU 13b. The timer 13e
is provided to perform interrupt processing and so on, and the I/O (13f)
is provided to exchange data between the CPU 13b and other devices.

[0095]The control signal input circuit 21 converts the solenoid-operated
valve driving signal SV (alternating current voltage signal: 200V-0V)
outputted from the temperature controller 10 into a binary signal of DC
voltage (DC5V-0V) and outputs the binary signal to the micro processor 13
as a signal indicating opened/closed state of the solenoid-operated valve
4.

[0096]The communication signal conversion circuit 22 is an interface
circuit to connect an external device such as personal computer (PC) 23
to the micro processor 13 via a connection cable 23a or the like, and is
disposed to input various setting values such as the set degree of
superheat Ts, the emergency valve opening SP and the others from the
operation of the PC 23. This circuit 22 performs mutual conversion of
signal's voltage level, the number of input and output terminals and the
like in accordance with differences between a signal format on the side
of the micro processor 13 and that on the side of the PC 23, for
instance, and the circuit 22 is composed of a RS-232C transceiver IC,
etc.

[0097]Next, the operation of the refrigeration cycle system 1 with the
construction described above will be explained. Here, at first, the
interrupt processing performed by the temperature controller 10 will be
explained with reference to FIGS. 1, 3. During the operation of the
system, the temperature controller 10 carries out a routine shown in FIG.
3 while using a timer (not shown) or the like at predetermined intervals
(every ten seconds, as an example).

[0098]When the interrupt processing is started, the temperature controller
10, as shown in FIG. 3, takes in the inside temperature Tis detected by
the inside temperature sensor 9 (Step S1), and judges whether or not the
inside temperature Tis is higher or equal to the ON set temperature Ton
(Step S2). At this time, for instance, in case that the inside
temperature Tis tends to increase and the inside temperature Tis is
higher or equal to the ON set temperature Ton (Step S2: Yes), the
compressor 2 is started (Step S3). At the same time, the
solenoid-operated valve 4 is opened to open the refrigerant flow passage
12a between the condenser 3 and the evaporator 6 (Step S4). This allows
the evaporator fan 6a to discharge a cold blast, which cools inside the
refrigeration and cold storage show case and decreases the inside
temperature Tis.

[0099]After that, when the inside temperature Tis gradually decreases and
the inside temperature Tis detected by the inside temperature sensor 9
becomes lower than the ON set temperature Ton (Step S2: No), the
temperature controller 10 judges whether or not the inside temperature
Tis is lower or equal to the OFF set temperature Toff (Step S5). As a
result, in case that the inside temperature Tis is higher than the OFF
set temperature Toff (Step S5: No), operation state (driving condition)
of the compressor 2 at the time is maintained to sequentially decrease
the inside temperature Tis. At this time, in the solenoid-operated valve
4 also, opened/closed state of the valve 4 at the time (opened state) is
maintained to sequentially open the refrigerant flow passage 12a.

[0100]Then, when the inside temperature Tis is sufficiently decreased and
the inside temperature Tis detected by the inside temperature sensor 9
becomes lower or equal to the OFF set temperature Toff (Step S5: Yes),
the operation of the compressor 2 is stopped, and the solenoid-operated
valve 4 is closed to close the refrigerant flow passage 12a as well
(Steps S8, S9). This stops cooling operation of the refrigeration and
cold storage show case and slowly increases the inside temperature Tis.

[0101]Afterward, the operations from Steps S1 to S9 described above are
repeated at ten second intervals, and when the inside temperature Tis
becomes higher or equal to the ON set temperature Ton again, operating
the compressor 2 and opening the solenoid-operated valve 4 are restarted
to decrease the inside temperature Tis.

[0102]Next, control operation performed by the degree-of-superheat
controller 11, particularly, operation of the micro processor 13
constituting a main part of the degree-of-superheat controller 11 will be
explained with reference to FIGS. 1, 2 and 4. In addition, this
procession is performed at ten second intervals also, for instance, in
the same manner as the control operation of the temperature controller 10
shown in FIG. 3.

[0103]When the interrupt processing is started, as shown in FIG. 4, the
micro processor 13 of the degree-of-superheat controller 11 takes in the
refrigerant temperature Tin at the inlet of the evaporator 6 (Step S11),
and the degree-of-superheat controller 11 judges whether or not a value
detected by the inlet temperature sensor 7 is abnormally high temperature
(for example exceeding 60°) (Step S12). This judgment processing
is performed to detect a short-circuit fault of the inlet temperature
sensor 7, in a thermistor, as an ambient temperature increases, a
resistance value thereof decreases, so that judging whether or not the
detected inlet temperature Tin is abnormally high is able to confirm
whether or not the resistance value of the inlet temperature sensor 7 is
extremely low.

[0104]As a result of the judgment, when the inlet temperature Tin exceeds
60° (Step S12: Yes) there is a fear that a short-circuit fault
occurs in the inlet temperature sensor 7, so that to the motor-driven
valve 5 is outputted the motor-driven valve driving signal EV to shift
the valve opening of the motor-driven valve 5 to the emergency valve
opening SP, and then, the valve 5 is stopped at the emergency valve
opening SP (Step S13).

[0105]Here, as described above, although the emergency valve opening SP
can arbitrarily be set with the input circuit 17, the PC 23 and the
others by users, in case that stoppage of cooling operation caused by the
fully-closed or the fully-opened states of the motor-driven valve 5
should be avoided to precede conservation of foods preserved inside, as
the emergency valve opening SP, it is preferable to set it as an
intermediate value (for instance 100 to 200 pulse) between the
fully-opened value and the fully-closed value. This can prevent stoppage
of circulating refrigerant and liquid back, which is generated when
extremely large amount of refrigerant is supplied to the evaporator 6,
which allows the refrigeration cycle system 1 to continuously be operated
under the condition that a certain cooling capacity is provided.

[0106]In this connection, for instance, in case that the refrigeration
cycle system 1 is operated using a stand-by sensor under the condition
that a temperature sensor can rapidly be repaired or replaced, as the
emergency valve opening SP, it is preferable that the valve opening of
the motor-driven valve 5 is set to be the fully-closed or the
fully-opened value. With this, the operation of the refrigeration cycle
system 1 can be stopped immediately in the stage that an abnormality
occurs in the temperature sensor and the abnormality can instantaneously
be informed.

[0107]On the other hand, when the inlet temperature Tin is below
60° (Step S12: No), the micro processor 13 judges whether or not
the inlet temperature Tin is abnormally low (for instance below
-60° (Step S14). This judgment processing is performed to detect
an open-circuit fault of the inlet temperature sensor 7, and judging
whether or not the detected inlet temperature Tin is abnormally low is
able to confirm whether or not the resistance value of the inlet
temperature sensor 7 is extremely high.

[0108]As a result of the judgment, in case that the inlet temperature Tin
is lower than -60° (Step S14: Yes), in the same manner as
described above, the motor-driven valve 5 is stopped at the emergency
valve opening SP, in accordance with usage of the refrigeration cycle
system 1, and foods inside the case is preserved and the inlet
temperature sensor 7 is promoted to be repaired or replaced (Step S13).

[0109]On the other hand, in case that the inlet temperature Tin is higher
or equal to -60° (Step S14: No), no abnormality is found in the
inlet temperature sensor 7, so that the refrigerant temperature Tout at
the outlet of the evaporator 6 is taken in (Step S15). Then, in the same
manner as the inlet temperature sensor 7, the micro processor 13 judges
whether or not a value detected by the outlet temperature sensor 8 is
abnormally high and whether or not it is abnormally low (Steps S16, S17).
As the results of the judgments, when an abnormality is found in the
outlet temperature sensor 8, the valve opening of the motor-driven valve
5 is shifted to the emergency valve opening SP, and the valve 5 is
stopped at the emergency valve opening SP (Step S13).

[0110]On the contrary, when no abnormality is found in the outlet
temperature sensor 8, a normal control operation of the valve opening is
started; the present degree of superheat Tsh (=Tout-Tin) is calculated;
and a deviation e(t) (=Ts-Tsh) between a set degree of superheat (target
value of the degree of superheat Tsh) and the present degree of superheat
is calculated (Steps S18, S19) as well. Next, based on a set of the
deviation e in the past, the proportional band PB, the integration time
Ti and the derivative time Td, the operation amount m(t) of the valve
opening at this time is calculated with a PID (proportional, integral and
differential) calculation in accordance with the following formula 1
(Step S20). Here, Kp is a proportional gain.

[0112]Then, the target valve opening of the motor-driven valve 5 is
calculated based on the calculated operation amount m(t) (Step S21), and
the degree-of-superheat controller 11 sets the number of driving pulses
such that the valve opening of the motor-driven valve 5 becomes the
target valve opening, and outputs the motor-driven valve driving signal
EV to the motor-driven valve 5 to increase/decrease the valve opening of
the valve 5 (Step S22).

[0113]Next, the whole stream of inputting (changing) operation of each
setting value with the input circuit 17 and the display circuit 18 shown
in FIG. 2 will be explained with reference to FIG. 5 and Table 1.
Meanwhile, FIG. 5 is an appearance diagram showing surface of a main body
of the degree-of-superheat controller 11.

[0114]For instance, under the condition that a temperature and the present
valve opening are respectively displayed on the temperature displaying
element 18a and the valve opening displaying element 18b, depressing the
set switch 17c enters the setting mode, and the temperature displaying
element 18a shifts from a temperature display mode to a setting value
display mode, and the valve opening displaying element 18b switches
display from the present valve opening to a setting item.

[0115]The setting value (numerical number) displayed on the temperature
displaying element 18a can be increased/decreased by depressing the up
switch 17a or the down switch 17b, and depressing the enter switch 17d
allows the displayed setting value to be renewed and stored as a new
setting value.

[0116]On the other hand, the setting items are, for example as shown in
Table 1, nine in number, and on the valve opening displaying element 18b
is displayed a setting value number and a symbol, for instance, "1. HV".
This setting item is, in the setting mode, by depressing the set switch
17c, sequentially switched to the next one, and when the setting item 9
("8. SP") is displayed, depressing the set switch 17c quits the setting
mode and returns to the condition that temperature and valve opening are
displayed.

[0117]Meanwhile, various setting values shown in the Table. 1, as
described above, can be set and changed by operations from the PC 23
utilizing communication also.

[0118]Next, inputting (changing) operation of each setting value with the
input circuit 17 and the display circuit 18 will be explained with
reference to FIGS. 5, 6.

[0119]When displaying a temperature on the temperature displaying element
18a (Step S31), in Step S32, whether or not the set switch 17c is
depressed is judged, and when depressed, in Step S33, on the temperature
displaying element 18a is displayed a setting value, and on the valve
opening displaying element 18b is displayed a number and a symbol
corresponding to the setting value as well, and it enters the setting
mode, when the set switch 17c is not depressed it returns to the
condition of Step S31.

[0120]Next, in Step S34, whether or not the up switch 18a is depressed is
judged, when depressed, in Step S35, whether or not displayed value on
the temperature displaying element 18a is the maximum value of the
setting value is judged. As a result of the judgment, when the displayed
value is not the maximum value of the setting value, in Step S36, the
displayed value is incremented and it returns to Step S34. On the other
hand, when the displayed value is the maximum value of the setting value,
it returns to Step S34 as it is.

[0121]In Step S34, when the up switch 17a is judged not to be depressed,
in Step S37, whether or not the down switch 17b is depressed is judged,
when depressed, in Step S38, whether or not the displayed value is the
minimum value of the setting value is judged, when the displayed value is
not the minimum value of the setting value, in Step S39, the displayed
value is decremented and it returns to Step S34. On the other hand, when
the displayed value is the minimum value of the setting value it returns
to Step S34 as it is.

[0122]In Step S37, when the down switch 17b is judged not to be depressed,
in Step S40, whether or not the enter switch 17d is depressed is judged,
when depressed, in Step S41, the setting value is renewed to the present
displayed value, and the renewed setting value is stored in the memory
circuit 20 of FIG. 2, and it returns to Step S34.

[0123]When the enter switch 17d is not depressed in Step S40, in Step S42,
whether or not the set switch 17c is depressed is judged, when judged not
to be depressed, it returns to Step S34.

[0124]In Step S42, when the set switch 17c is judged to be depressed, in
Step S43, whether or not the setting is finished is judged. Concretely,
in Step S42, under the condition that the setting item 9 "emergency valve
opening" is displayed, when the set switch 17c is depressed the setting
mode is judged to be finished in Step S43, and it returns to Step S31.

[0125]On the other hand, in Step S42, under the condition that an item
other than the setting item 9 "emergency valve opening" is selected, when
the set switch 17c is depressed, in Step S44, the next setting value is
displayed on the temperature displaying element 18a; a number and a
symbol corresponding to the next setting are displayed on the valve
opening displaying element 18b; it returns to Step S34; and the above
motions are repeated.

[0126]The above operations are able to input (change) each setting value,
and the emergency valve opening SP can freely be set also. In addition,
the emergency valve opening SP can freely be set also after it was set
once, further, the set emergency valve opening SP can be changed not only
during the stoppage of the refrigeration cycle system 1 but also during
the operation of the system 1.

[0127]As described above, with the present embodiment, as the emergency
valve opening SP of the motor-driven valve 5, intermediate valve opening
values excluding those in the fully-opened and fully-closed states can be
set, in addition to that, in case that an abnormality occurs in the inlet
and outlet temperature sensors 7, 8, the motor-driven valve 5 is stopped
at the set emergency valve opening SP, so that even if an abnormality
occurs in the sensors 7, 8, stoppage of the refrigeration cycle system 1
due to a low-pressure abnormality and liquid back can be avoided. This
can continue cooling operation inside the case until a maintenance worker
arrives, which prevents bruised foods even if swift repair is impossible.

[0128]Further, since the emergency valve opening SP can freely be changed,
the emergency valve opening SP can be set in accordance with usage of the
refrigeration cycle system 1 and user's request thereto, for instance,
besides the control specifying the valve opening to the intermediate
valve opening values, a control intentionally stop the system 1 is also
selectable. This can increase degree of freedom in selecting motion of
the motor-driven valve 5, and improve versatility and convenience of the
refrigeration cycle system 1.

[0129]In addition, in the present embodiment described above, although the
case that an abnormality occurs in the inlet and outlet temperature
sensors 7, 8 is exemplified, the present invention can be applied to a
sensor detecting a temperature at the valve opening control of the
motor-driven valve 5 other than the inlet and outlet temperature sensors
7, 8, moreover, the present invention can be applied also when an
abnormality occurs in a pressure sensor detecting pressure of the
refrigerant circulating in the refrigeration cycle.

[0130]Next, a valve controller according to the second embodiment of the
present invention will be explained with reference to FIGS. 7 to 11. In
FIGS. 7, 8, like symbols are applied to like constituents shown in FIGS.
1, 2, and detailed explanation thereof will be omitted.

[0131]Further, in the present embodiment also, as a refrigeration cycle
system is exemplified a system for controlling temperature inside a
refrigeration and cold storage showcase used for cold reserving and
displaying foods, in addition, the valve controller of the present
invention is exemplarily used for a device for controlling an electric
expansion valve (motor-driven valve) disposed in the above refrigeration
cycle system described above.

[0132]FIG. 7 shows the refrigeration cycle system with the valve
controller according to the second embodiment, and the system 30 is
provided with the compressor 2, the condenser 3, the condenser fan 3a,
the solenoid-operated valve 4, the motor-driven valve 5, the evaporator
6, the evaporator fan 6a, the inlet temperature sensor 7, the outlet
temperature sensor 8, the inside temperature sensor 9, the temperature
controller 10 and a degree-of-superheat controller 31.

[0133]The degree-of-superheat controller 31 is a control circuit for
controlling valve opening of the motor-driven valve 5, and is constructed
by a microcomputer and peripheral circuits for instance. This controller
31 calculates valve opening of the motor-driven valve 5 through PID
control based on the degree of superheat Tsh of the refrigerant in the
evaporator 6 (Tsh=the temperature Tout detected by the outlet temperature
sensor 8-the temperature Tin detected by the inlet temperature sensor 7),
and outputs the motor-driven valve driving signal EV corresponding to the
calculated valve opening to the pulse motor of the motor-driven valve 5.

[0134]In addition, the degree-of-superheat controller 31 has functions of
detecting opened/closed states of the solenoid-operated valve 4 by
monitoring a voltage level of the solenoid-operated valve driving signal
SV, and switching presence/absence of an output of the motor-driven valve
driving signal EV to the motor-driven valve 5 in accordance with the
opened/closed states of the solenoid-operated valve 4. Further the
controller 31 has a function of controlling an initialization processing
of the motor-driven valve 5 also, and controls execution timings of the
initialization processing (hereinafter called as "initialization timing")
in accordance with opening/closing timings of the solenoid-operated valve
4 and time measured by a timer described below.

[0135]Meanwhile, a setting value determining the initialization timing
(initialization time It), in the same manner as "the emergency valve
opening SP" in the first embodiment, can be inputted with the input
circuit 17, or inputted by operating the PC 23 through the communication
signal conversion circuit 22. Further, specific input and change
operations of the initialization time It are performed in the same manner
as shown in FIGS. 5 and 6.

[0137]The inlet temperature detecting circuit 34 is a resistance-voltage
conversion circuit for converting a resistance value of the inlet
temperature sensor 7 to a DC-voltage signal and outputting it to the
micro processor 13. In order to accurately detect the temperature Tin of
a refrigerant at the inlet of the evaporator 6, this inlet temperature
detecting circuit 34 is constructed by a bridge circuit 34a and an
amplifying circuit 34b for amplifying a voltage between intermediate
terminals of the bridge circuit 34a.

[0138]The outlet temperature detecting circuit 35 is a resistance-voltage
conversion circuit for converting a resistance value of the outlet
temperature sensor 8 to a DC-voltage signal and outputting it to the
micro processor 13. This outlet temperature detecting circuit 35 is also
constructed by a bridge circuit 35a and an amplifying circuit 35b to
accurately detect the temperature Tout of a refrigerant at the outlet of
the evaporator 6.

[0139]Next, the operation of the refrigeration cycle system 30 with the
construction described above will be explained.

[0140]The interrupt processing performed by the temperature controller 10
is carried out in the same manner as the first embodiment, and the
routine shown in the FIG. 3 while using a timer (not shown) and the like
is performed at predetermined intervals (every ten seconds, as an
example).

[0141]Next, a control operation performed by the degree-of-superheat
controller 31, particularly, operation of the micro processor 13
constituting a main part of the controller 31 will be explained. Here, at
first, management processing of the initialization timing will be
explained with reference to FIGS. 7 to 9. Meanwhile, this procession is
different from the control operation of the temperature controller 10
shown in FIG. 3, and is continuously performed while the refrigeration
cycle system 30 is in operation.

[0142]As shown in FIG. 9, when power is supplied to start operation of the
refrigeration cycle system 30 (Step S51), the micro processor 13 sets the
initialization time It, which is set by the input circuit 17 or the PC
23, to a start value (at a down count) of the timer 13e (Step S52).

[0143]Next, an initialization flag Fi is cleared (set it to "0") (Step
S53), and the down count of the timer 13e is started as well (Step S54).
Here, the initialization flag Fi shows necessity of the initialization
processing of the motor-driven valve 5, and in case that the value of the
flag Fi is "1", the flag Fi shows that the initialization processing
should be carried out, and in case that the value of the flag Fi is "0",
which means the initialization processing is not required.

[0144]After that, the down count is continued until the count value of the
timer 13e reaches to "0" (Step S55), and when the count value reaches to
"0" (time up) (Step S55: Yes), the initialization flag Fi is set to be
"1" (Step S56). Then, the initialization time It is set to the start
value of the timer 13e again (Step S57), and the down count of the timer
13e is started (Step S58).

[0145]Hereinafter, until a power source is turned off to stop the
operation of the refrigeration cycle system 30, the processes in the
Steps S55 to S58 are repeated (Step S59) to continuously manage the
initialization timing.

[0146]Next, an interrupt processing performed by the degree-of-superheat
controller 31 will be explained with reference to FIGS. 7, 8 and 10.
Meanwhile, this procession is carried out in synchronization with the
control operation of the temperature controller 10 at ten second
intervals, for instance, in the same manner as the control operation of
the temperature controller 10 thereof shown in FIG. 3.

[0147]When the interrupt processing is started, as shown in FIG. 10, the
micro processor 13 of the degree-of-superheat controller 31 judges
whether or not the solenoid-operated valve 4 is opened with reference to
opening/closing signals (a convert signal of the solenoid-operated valve
driving signal SV) outputted from the control signal input circuit 21
(Step S61). As a result of the judgment, in case that the valve 4 is
opened (Step S61: Yes), the degree-of-superheat controller 31 takes in
refrigerant temperatures Tin, Tout at the inlet and outlet of the
evaporator 6 respectively (Steps S62 and S63) to calculate the present
degree-of-superheat Tsh (=Tout-Tin) (Step S64).

[0148]Next, a deviation e(t) (=Ts-Tsh) between a set degree-of-superheat
(target value of the degree of superheat Tsh) Ts and the present
degree-of-superheat Tsh is calculated (Step S65), and based on a set of
the deviation e in the past, the proportional band PB, the integration
time Ti and the derivative time Td, the operation amount m(t) of the
valve opening at this time is calculated with a PID (proportional,
integral and differential) calculation in accordance with the above
formula 1 (Step S66).

[0149]This calculates a target valve opening that the motor-driven valve 5
should reach to, and the degree-of-superheat controller 31 specifies the
number of driving pulses such that a valve opening of the valve 5 becomes
the target valve opening, and outputs the motor-driven valve driving
signal EV to the valve 5 to increase/decrease the valve opening of the
valve 5 (Step S67).

[0150]On the other hand, as a result of the above judgment in Step S61, in
case that the solenoid-operated valve 4 is closed (Step S61: No), the
micro processor 13 judges whether or not the initialization flag Fi is
set to be "1" (Step S68). As the result, in case that the initialization
flag Fi is set to be "0" (Step S68: No), any procession is not performed,
and changing the valve opening of the motor-driven valve 5 and the like
are not carried out.

[0151]On the contrary, in case that the initialization flag Fi is set to
be "1" (Step S68: Yes), the micro processor 13 judges whether or not the
target valve opening of the motor-driven valve 5 is set to be a -α
pulse (Step S69). Here, "-α pulse" is a valve opening value to
allow the motor-driven valve 5 to be driven in a closing direction and to
be in the fully-closed state. Meanwhile, although a valve opening value
in the fully-closed state is usually 0 pulse, the target valve opening
value is set to be -α pulse (minus value). This is because in view
of catching of a foreign matter or the like, to the valve opening value
in the fully-closed state (0 pulse) is added a margin of a few pulses
(approximately 8 pulses as an example) in a direction that the valve 5
closes (see FIG. 11 (g)). In addition, in the Step S69, the reason why
the micro processor 13 judges whether or not the target valve opening is
set to -α pulse is to judge whether or not the initialization
processing of the valve 5 has already been started.

[0152]In the case described above, for example, when the initialization
processing of the motor-driven valve 5 has not yet been started, and the
target valve opening of the valve 5 is set to the valve opening
calculated in the Steps S66, S67 (Step S69: No), it moves to Step S70,
and the valve opening Pi of the valve 5 at the time is memorized to the
RAM 13d inside the micro processor 13 as a valve opening Pm just before
the initialization processing is performed. Next, the target valve
opening of the valve 5 is set to -α pulse (Step S71), and the
initialization processing is started (Step S72).

[0153]Under the condition, when an interrupt time (ten seconds) passes,
the micro processor 13 judges whether or not the target valve opening of
the motor-driven valve 5 is set to be -α pulse again (Step S69). At
this moment, since the initialization processing of the motor-driven
valve 5 has already been started, it moves to Step S73, and the micro
processor 13 judges whether or not the valve opening Pi of the valve 5 at
the moment is set to be -α pulse. Meanwhile, the reason why the
judgment processing in Step S73 is performed is to judge whether or not
the initialization processing started in Step S72 is finished.

[0154]Then, in case that the valve opening Pi reaches to the -α
pulse after the initialization processing is finished (Step S73: Yes),
the target valve opening of the motor-driven valve 5 is set to be the
valve opening Pm memorized in the RAM 13d in the previous Step S70
described above (Step S74). Next, the valve 5 is driven (Step S75), and
the initialization flag Fi is set to be "0" (Step S76).

[0155]In this connection, when the initialization processing has not yet
been finished and the valve opening Pi of the motor-driven valve 5 has
not reached to -α pulse at the judgment processing in the Step S73
(Step S73: No), the initialization processing is continued (Step S77).

[0156]Next, an example of operation of the refrigeration cycle system 30
under the control shown in FIGS. 3, 9 and 10 will be explained with
reference to FIG. 11. Here, the initialization time It shall be set to be
168 hours (24 hours×7(=one week)). In addition, operation of the
refrigeration cycle system 30 is started at the time earlier than the
timing t1 shown in FIG. 11, and the clear processing of the
initialization flag Fi and the count start of the timer 13e at the
power-supply shall have been already started.

[0157]As shown in the FIG. 11, in the timing t1, when the inside
temperature Tis becomes higher or equal to the ON set temperature Ton,
the compressor 2 is operated and the solenoid-operated valve 4 is opened
to open the refrigerant flow passage 12a. Further, in response to the
opening the solenoid-operated valve 4, the opening/closing signal
(control signal) becomes DC-5V, which starts the valve opening adjustment
of the motor-driven valve 5 based on a PID calculation so as to adjust
flow rate of a refrigerant circulating in the refrigeration cycle. The
operation of the compressor 2, the opening of the solenoid-operated valve
4 and the valve opening adjustment of the motor-driven valve 5 are
continuously performed until the inside temperature Tis is higher than
the OFF set temperature Toff even if the inside temperature Tis becomes
lower or equal to the ON set temperature Ton.

[0158]Then, the temperature inside the refrigeration and cold storage show
case decreases, and in the timing t2, when the inside temperature Tis
reaches to the OFF set temperature Toff, the operation of the compressor
2 is stopped and the solenoid-operated valve 4 is closed to close the
refrigerant flow passage 12a. In addition, in response to the closing the
solenoid-operated valve 4, the opening/closing signal (control signal)
becomes 0V, which stops outputting the motor-driven valve driving signal
EV to the motor-driven valve 5 (the number of driving pulses is set to be
zero) and suspends the valve opening adjustment of the valve 5. As a
result, the valve opening of the motor-driven valve 5 remains as that at
the stopping of the valve opening adjustment, hereinafter, until the
valve opening adjustment is restarted, the condition is maintained.

[0159]After that, the temperature inside the refrigeration and cold
storage show case increases, and in the timing t3, when the inside
temperature Tis reaches to the ON set temperature Ton again, the
operation of the compressor 2 is restarted and the solenoid-operated
valve 4 is opened. At this moment, the opening/closing signal (control
signal) becomes DC-5V also, which restarts the valve opening adjustment
of the motor-driven valve 5, however, the valve opening of the valve 5 at
the restarting remains as that at the stoppage of the valve opening
adjustment (in the timing t2), so that increase/decrease of the valve
opening of the valve 5 after restarting the operation of the compressor 2
starts from the valve opening at the stoppage of the valve opening
adjustment.

[0160]Therefore, the operation amount of the motor-driven valve 5 in the
above case is calculated by deducting the valve opening at the stoppage
of the valve opening adjustment from the target valve opening calculated
by the PID operation, so that, for instance, the operation amount of the
motor-driven valve 5 can considerably be decreased in comparison to a
case when shifted to a target valve opening from the fully-closed state.
As a result, it is possible to keep the number of driving pulses of the
motor-driven valve driving signal EV small to make the operation amount
of the motor-driven valve 5 small, resulting in longer life of the valve
5.

[0161]Next, in the timing t4, when 168 hours passes after starting count
with the timer 13e and the count value of the timer 13e reaches to "0",
the initialization flag Fi is set to be "1", which sets that
initialization of the motor-driven valve 5 shall be carried out.

[0162]After that, in the timing t5, the inside temperature Tis decreases
and the temperature Tis becomes lower or equal to the OFF set temperature
Toff the operation of the compressor 2 is stopped and the
solenoid-operated valve 4 is closed. In response to this, the
opening/closing signal (control signal) becomes 0V, which leads a period
that the valve control of the motor-driven valve 5 stops, so that in the
motor-driven valve 5, the initialization processing is started to
determine the position of the valve body. Meanwhile, although the target
valve opening when performing the initialization processing is set to be
-α pulse as described above, the valve body of the motor-driven
valve 5 contact with a stopper (not shown) provided inside the
motor-driven valve 5 when reaching to the fully-closed position, so that
motion of the valve body is mechanically restricted, and the valve body
does not move any more in a direction that the valve 5 closes.

[0163]Then, when the initialization processing is finished, after that, in
the timing t6, the valve opening of the motor-driven valve 5 is changed
to that just before performing the initialization processing, and the
initialization flag Fi is set to be "0" as well.

[0164]Hereinafter, while the refrigeration cycle system 30 is in
operation, the same operation is repeated, that is, the initialization
processing of the motor-driven valve 5 is performed each time that the
initialization flag Fi is set to be "1" and the solenoid-operated valve 4
is closed.

[0165]In addition, in the operation exemplified above, the
solenoid-operated valve 4 is closed after the time measured by the timer
13e reaches to the initialization time It (see the timings t4, t5), so
that the initialization processing of the motor-driven valve 5 is
performed after the solenoid-operated valve 4 is closed, on the other
hand, in case that the solenoid-operated valve 4 is closed, reaching the
time measured by the timer 13 to the initialization time It allows the
initialization processing to instantly be carried out.

[0166]As described above, in the present embodiment, the initialization
time It can be set, in addition to that, each time that the time measured
by the timer 13e reaches to the initialization time It the initialization
processing of the motor-driven valve 5 is performed, so that not only at
the power-up but after that, the initialization processing can
periodically be carried out. As a result, even when a difference in valve
opening caused by catching of a foreign substance or the like is
generated in operation of the refrigeration cycle system 30, the
difference can periodically be modified, which allows the valve opening
of the motor-driven valve 5 to accurately be controlled. Therefore, it is
possible to prevent failures such as leakage of a refrigerant beforehand,
consequently, the reliability of the refrigeration and cold storage
system can be improved.

[0167]In addition, the initialization processing of the motor-driven valve
5 is performed only when the refrigerant flow passage 12a is closed after
the solenoid-operated valve 4 is closed and the valve opening control of
the motor-driven valve 5 through PID control is stopped, so that even
while the refrigeration cycle system 30 is in operation, it is possible
to perform the initialization processing without harmful affects to the
motor-driven valve 5 and other devices connected with the motor-driven
valve 5 (the compressor 2 and the like). Therefore, it is unnecessary to
stop the refrigeration cycle system 30 for the initialization processing,
which allows hindrance to the operation of the refrigeration cycle system
30 to be avoided and complexity accompanying the operation to be
eliminated.

[0168]Next, a refrigeration and cold storage system and a controller of
the system according to the third embodiment of the present invention
will be explained with reference to FIGS. 12 to 14. In FIG. 12, to the
same constituent factors as those in FIG. 1 are attached the same
symbols, and explanations thereof will be omitted. And, in the following
explanation, the refrigeration and cold storage system according to the
present invention is exemplarily applied to a refrigeration and cold
storage showcase used for cold reserving and displaying foods, and the
like.

[0169]FIG. 12 shows the refrigeration and cold storage system according to
the third embodiment of the present invention, this system 40 is provided
with the compressor 2, the condenser 3, the condenser fan 3a, the
solenoid-operated valve 4, the motor-driven valve (motor-driven expansion
valve) 5, the evaporator 6, the evaporator fan 6a, the inlet temperature
sensor 7, the outlet temperature sensor 8, the inside temperature sensor
9, the temperature controller 10, and a degree-of-superheat controller
41.

[0170]The degree-of-superheat controller 41 is a control circuit for
controlling valve opening of the motor-driven valve 5, and is constructed
by a microcomputer and peripheral circuits for instance. This controller
41 calculates valve opening of the motor-driven valve 5 through PID
control based on the degree of superheat Tsh of the refrigerant in the
evaporator 6 (Tsh=the temperature Tout detected by the outlet temperature
sensor 8-the temperature Tin detected by the inlet temperature sensor 7),
and outputs the motor-driven valve driving signal EV corresponding to the
calculated valve opening to the pulse motor of the motor-driven valve 5.

[0171]In addition, the degree-of-superheat controller 41 has functions of
detecting opened/closed state of the solenoid-operated valve 4 by
monitoring a voltage level of the solenoid-operated valve driving signal
SV, and switching presence/absence of an output of the motor-driven valve
driving signal EV to the motor-driven valve 5 in accordance with the
opened/closed state of the solenoid-operated valve 4.

[0172]Next, the operation of the refrigeration and cold storage system 40
with the above-mentioned construction will be explained.

[0173]Interrupt processing by the temperature controller 10 is carried out
in the same manner as the first embodiment, and the routine shown in the
FIG. 3 while using a timer (not shown) and the like is performed at
predetermined intervals (every ten seconds, as an example).

[0174]Next, control operation performed by the degree-of-superheat
controller 41 will be explained with reference to FIGS. 12, 13. The
degree-of-superheat controller 41 operates in synchronization with the
operation of the temperature controller 10, and in the same manner as the
controller 10, for instance, the degree-of-superheat controller 41
performs a routine shown in the FIG. 13 every ten seconds, as an example.

[0175]When the interrupt processing is started, as shown in FIG. 13, the
degree-of-superheat controller 41 firstly references the
solenoid-operated valve driving signal SV outputted from the temperature
controller 10, and judges whether or not the solenoid-operated valve 4 is
opened. As a result of the judgment, in case that the valve 4 is opened
(Step S81: Yes), the degree-of-superheat controller 41 takes in
refrigerant temperatures Tin, Tout at the inlet and outlet of the
evaporator 6 respectively (Steps S82, S83) to calculate the present
degree-of-superheat Tsh (=Tout-Tin) (Step S84).

[0176]Next, a deviation e(t) (=Ts-Tsh) between a set degree-of-superheat
(target value of the degree of superheat Tsh) Ts and the present
degree-of-superheat Tsh is calculated (Step S85), and based on a set of
the deviation e in the past, the proportional band PB, the integration
time Ti and the derivative time Td, the operation amount m(t) of the
valve opening is calculated with a PID (proportional, integral and
differential) calculation in accordance with the above formula 1 (Step
S86).

[0177]This calculates a target valve opening that the motor-driven valve 5
should reach to, and the degree-of-superheat controller 41 specifies the
number of driving pulses such that a valve opening of the valve 5 becomes
the target valve opening, and outputs the motor-driven valve driving
signal EV to the valve 5 to increase/decrease the valve opening of the
valve 5 (Step S87).

[0178]On the other hand, as a result of the above judgment in Step S81, in
case that the solenoid-operated valve 4 is closed (Step S81: No), any
procession is not performed, and changing the valve opening of the
motor-driven valve 5 and the like are not carried out.

[0179]Next, operations of the solenoid-operated valve 4 and the
motor-driven valve 5, when operation/stoppage of the compressor 2 is
switched, will be exemplarily explained mainly with reference to FIG. 14.

[0180]In the timing t1, when the inside temperature Tis becomes higher or
equal to the ON set temperature Ton, the compressor 2 is operated and the
solenoid-operated valve 4 is opened to open the refrigerant flow passage
12a. Further, in response to the opening the solenoid-operated valve 4,
the valve opening adjustment of the motor-driven valve 5 based on a PID
calculation is started to adjust flow rate of a refrigerant circulating
in the refrigeration cycle. The operation of the compressor 2, the
opening of the solenoid-operated valve 4 and the valve opening adjustment
of the motor-driven valve 5 are continuously performed until the inside
temperature Tis is higher than the OFF set temperature Toff even if the
inside temperature Tis becomes lower or equal to the ON set temperature
Ton.

[0181]Then, the temperature inside the refrigeration and cold storage show
case decreases, and in the timing t2, when the inside temperature Tis
reaches to the OFF set temperature Toff, the operation of the compressor
2 is stopped and the solenoid-operated valve 4 is closed to close the
refrigerant flow passage 12a. In addition, in response to the closing the
solenoid-operated valve 4, outputting the motor-driven valve driving
signal EV to the motor-driven valve 5 is stopped (the number of driving
pulses is set to be zero), and the valve opening adjustment of the valve
5 is suspended. As a result, the valve opening of the motor-driven valve
5 remains as that at the stoppage of the valve opening adjustment,
hereinafter, until the valve opening adjustment is restarted, the
condition is maintained.

[0182]After that, the temperature inside the refrigeration and cold
storage show case increases, and in the timing t3, when the inside
temperature Tis reaches to the ON set temperature Ton again, the
operation of the compressor 2 is restarted and the solenoid-operated
valve 4 is opened. At this moment, the valve opening adjustment of the
motor-driven valve 5 is restarted, however, the valve opening of the
valve 5 at the restarting remains as that at the stoppage of the valve
opening adjustment (in the timing t2), so that increase/decrease of the
valve opening of the valve 5 after restarting the operation of the
compressor 2 starts from the valve opening at the stoppage of the valve
opening adjustment.

[0183]Therefore, the operation amount of the motor-driven valve 5 in the
above case is calculated by deducting the valve opening at the stoppage
of the valve opening adjustment from the target valve opening calculated
by the PID operation, so that, for instance, the operation amount of the
motor-driven valve 5 can considerably be decreased in comparison to a
case when shifted to a target valve opening from the fully-closed state.
As a result, it is possible to keep the number of driving pulses of the
motor-driven valve driving signal EV small, which allows the consumption
of the number of driving pulses accompanying the switching of
operation/stoppage of the compressor 2 to sharply be reduced.

[0184]As mentioned above, in the embodiment, the solenoid-operated valve 4
is mounted between the condenser 3 and the evaporator 6, in addition to
that, when the operation of the compressor 2 is stopped, the
solenoid-operated valve 4 is closed and the valve opening of the
motor-driven valve 5 is maintained as that at the stoppage of the
operation of the compressor 2 as well, and when the operation of the
compressor 2 is restarted, the solenoid-operated valve 4 is opened and
the valve opening control of the motor-driven valve 5 is started from the
valve opening at the stoppage of the operation of the compressor 2 as
well, which makes the fully-closing operation of the motor-driven valve 5
when stopping the compressor 2 and the opening operation of the
motor-driven valve 5 when starting the compressor 2 unnecessary, while
preventing the inside temperature from rising when the operation of the
compressor 2 is stopped.

[0185]As a result, it becomes unnecessary to largely change the valve
opening of the motor-driven valve 5 each time that the operation/stoppage
of the compressor 2 is switched, which remarkably reduces the consumption
of the number of driving pulses. This allows the life of the motor-driven
valve 5 to be lengthened, consequently, the reliability of the
refrigeration and cold storage system to be improved.

[0186]The embodiments of the present invention are explained above,
however, this invention is not limited to the above constructions, and
various changes can be made in the scope of the invention described in
claims.

[0187]For example, in the first to the third embodiments, although systems
controlling the temperature inside of a refrigeration and cold storage
showcase are shown as the refrigeration cycle systems 1, 30 and 40, this
invention can widely be applied to other temperature adjustment systems
such as air conditioners.

[0188]Moreover, in the first to the third embodiments, valve opening of an
expansion valve is controlled in a refrigeration cycle, as an example,
however, this invention can also be applied to control of a flow control
valve (motor-driven valve) in a hot gas by-pass circuit of a
refrigeration cycle.

[0189]Furthermore, in the first and second embodiments, although wired
communication is exemplified as a type of communication between the
microprocessors 13 of the degree-of-superheat controllers 11, 31 and the
PCs 23, it may be possible to utilize radio communication for connecting
the microprocessors 13 and the PCs 23. This is also applicable to the
microprocessor (not shown) of the degree-of-superheat controller 41
according to the third embodiment.

[0190]In the first to the third embodiments, the solenoid-operated valve 4
is disposed upstream of the motor-driven valve 5 (between the condenser 3
and the motor-driven valves 5), so long as between the condenser 3 and
the evaporator 6, the position where the solenoid-operated valve 4 is
disposed is not limited in particular, and the valve 4 may be disposed
downstream of the motor-driven valve 5 (between the motor-driven valve 5
and the evaporator 6).

[0191]Further, in the first to the third embodiments, though the
temperature controller 10 and the degree-of-superheat controllers 11, 31,
41 are separately constructed for convenience of explanation, these
controllers can be integrated as a single microcomputer and others. In
such a case, information on opened/closed state of the solenoid-operated
valve 4 from the temperature controller 10 toward the degree-of-superheat
controllers 11, 31, and 41 (the solenoid-operated valve driving signal
SV) can be managed through inner procession of the microcomputer.

[0192]Although outputting the solenoid-operated valve driving signal SV to
the degree-of-superheat controller 41 allows opened/closed state of the
solenoid-operated valve 4 to be informed to the degree-of-superheat
controller 41 in the first to the third embodiments, the
solenoid-operated valve driving signal SV is not always used, but other
signal capable of informing the opened/closed state of the
solenoid-operated valve 4 can be outputted to the degree-of-superheat
controller 41.

[0193]Still further, in the first to the third embodiments, valve opening
of the motor-driven valve 5 is exemplarily controlled by PID control, in
addition to that, P (proportional) control, PI (proportional and
integral) control, or PD (proportional and differential) control can be
used.